Stupid question, but just double-checking. I'm calibrating a new mash-tun I've created (50qt Coleman w/SS braided hose manifold) and questioned myself on the infusion temp setting. Is this asking for the water temp PRIOR to actually dumping it into the mash-tun (which I think is right), or is it the temp of the water immediately AFTER I've dumped the water in. I know if sounds silly, but I just wanted to double-check. Let me know.

I mash in a different way. I use a pot as a mash-tun, heat the water with it and then dump the grist. The major difference is that the mash-tun is heated. I am not sure how to calibrate the vessel this way; it is certainly not as suggested in BTP (to dump the hot water into the vessel which is at room temp). Maybe I should just heat the vessel with water to the specified temperature, turn off the heat, and then measure the temperature again. Does that sound right?

I'm doing the same thing right now.
1. I've just calibrated a kettle (not as a heat source). Approx 47C water went to 42C when I put it in.. but this doesn't really matter, as I use immersion elements to heat water in here. So I heated my water (taking temperature measurements along the way to calibrate my heat source).. then stopped at 75C, and removed all heat sources, and calibrated from there. I used 18L of water to do this (just a hair under 5 gallons).

My mash tun is next..
I know it will drop about 5C from the time it leaves my kettle (which I use to heat all my water) to the time it gets into the mash tun/esky. I always account for this anyway.. So do I Use the last temp as it was in the kettle as my INFUSION TEMP. as T=0.. and wear all the temperature drop during the transfer, and the cooling effect when it hits the mash tun.. with t=5min being significantly lower than it would for a pre-warmed mash tun?? Or do I treat it as pre-warmed, once it is in the Esky as T=0.. ? The numbers will be VERY different!!

It would be easier if there was a T=0 being in the kettle.. t=5min for a transfer/vessel heating shift, then t=10min for a short-term thermal mass loss.. or something. then a t=65 for whatever else.